U.S. patent application number 11/386804 was filed with the patent office on 2006-10-12 for image forming apparatus.
This patent application is currently assigned to CANON KABUSHIKI KAISHA. Invention is credited to Takako Hanada, Kuniyasu Kimura, Hiroto Nishihara, Naoto Watanabe, Yukio Yokoyama.
Application Number | 20060227205 11/386804 |
Document ID | / |
Family ID | 37063951 |
Filed Date | 2006-10-12 |
United States Patent
Application |
20060227205 |
Kind Code |
A1 |
Nishihara; Hiroto ; et
al. |
October 12, 2006 |
Image forming apparatus
Abstract
An image forming apparatus includes a control unit for
controlling a plurality of fixing units independently of one
another regardless of a state of an image forming unit, and a
receiving unit for receiving image forming requests, and has a
control sequence, in which when not all of a recording medium
material, a recording medium state, environment, and image data
satisfy predetermined conditions, at least one of the plurality of
fixing units are caused to operate, and a control sequence, in
which when it is detected that an image forming request, for which
all of the plurality of fixing units are required, is received by
the receiving unit, each currently unused fixing unit is caused to
operate. Accordingly, it is possible to realize high productivity
even when there exist fixing units not driven due to the recording
medium physical properties, recording medium state, environment,
image data, or the like.
Inventors: |
Nishihara; Hiroto;
(Toride-shi, JP) ; Watanabe; Naoto; (Kashiwa-shi,
JP) ; Yokoyama; Yukio; (Sakado-shi, JP) ;
Kimura; Kuniyasu; (Toride-shi, JP) ; Hanada;
Takako; (Yokohama-shi, JP) |
Correspondence
Address: |
FITZPATRICK CELLA HARPER & SCINTO
30 ROCKEFELLER PLAZA
NEW YORK
NY
10112
US
|
Assignee: |
CANON KABUSHIKI KAISHA
TOKYO
JP
|
Family ID: |
37063951 |
Appl. No.: |
11/386804 |
Filed: |
March 23, 2006 |
Current U.S.
Class: |
347/194 |
Current CPC
Class: |
G03G 15/2021 20130101;
G03G 15/2039 20130101 |
Class at
Publication: |
347/194 |
International
Class: |
B41J 2/00 20060101
B41J002/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 8, 2005 |
JP |
2005-112160(PAT.) |
Claims
1. An image forming apparatus, comprising: a first image heating
member for heating an image on a recording material; a second image
heating member for heating the image on the recording material
heated by the first image heating member; image forming condition
selection means for making a selection from among a first image
forming condition, under which the image on the recording material
is heated by the first image heating member without being heated by
the second image heating member, and a second image forming
condition under which the image on the recording material is heated
by the first image heating member and then is heated by the second
image heating member; first temperature control means for
controlling a temperature of the first image heating member; second
temperature control means for controlling a temperature of the
second image heating member to a set temperature during image
formation under the second image forming condition and capable of
controlling the temperature of the second image heating member to a
temperature lower than the set temperature in image formation under
the first image forming condition; decision means for, in a case
where an image forming signal corresponding to the second image
forming condition is inputted during a job of image formation under
the first image forming condition, deciding a timing to start
control of a temperature of the second image heating member to said
set temperature on the basis of the amount of processes which are
necessary until completing the job.
2. An image forming apparatus according to claim 1, wherein the
timing is retarded as the time interval between the input of the
image forming signal and completion of the image formation is
increased.
3. An image forming apparatus according to claim 1, wherein the
timing is advanced as a difference between the temperature of the
second image heating member at the time of the input of the image
forming signal and the set temperature is increased.
4. An image forming apparatus according to claim 1, further
comprising calculating means for calculating a time taken to raise
the temperature of the second image heating member at the time of
the input of the image forming signal to the set temperature,
wherein the timing is decided using the time obtained from the
calculating means and an expected time between the input of the
image forming signal and completion of the image formation.
5. An image forming apparatus according to claim 1, wherein, when
the expected time is shorter than the time obtained from the
calculating means, the timing is decided so that the control of the
temperature of the second image heating member for the inputted
image forming signal is started concurrently with the input of the
image forming signal.
6. An image forming apparatus according to claim 1, wherein, when
the expected time is longer than the time obtained from the
calculating means, the timing is decided so that the temperature of
the second image heating member is kept at the temperature lower
than the set temperature since the image forming signal is inputted
so that the temperature of the second image heating member and then
is raised to the set temperature before the completion of the image
formation.
7. An image forming apparatus, comprising: a first image heating
member for heating an image on a recording material; a second image
heating member for heating the image on the recording material
heated by the first image heating member; image forming condition
selection means for making a selection from among a first image
forming condition, under which the image on the recording material
is heated by the first image heating member without being heated by
the second image heating member, and a second image forming
condition under which the image on the recording material is heated
by the first image heating member and then is heated by the second
image heating member; first temperature control means for
controlling a temperature of the first image heating member; second
temperature control means for controlling a temperature of the
second image heating member to a set temperature during image
formation under the second image forming condition and turning off
under the first image forming condition; decision means for, in a
case where an image forming signal corresponding to the second
image forming condition is inputted during a job of image formation
under the first image forming condition, deciding a timing to start
control of a temperature of the second image heating member to said
set temperature on the basis of the amount of processes which are
necessary until completing the job.
8. An image forming apparatus according to claim 7, wherein the
timing is retarded as the time interval between the input of the
image forming signal and completion of the image formation is
increased.
9. An image forming apparatus according to claim 7, wherein the
timing is advanced as a difference between the temperature of the
second image heating member at the time of the input of the image
forming signal and the set temperature is increased.
10. An image forming apparatus according to claim 1, further
comprising calculating means for calculating a time taken to raise
the temperature of the second image heating member at the time of
the input of the image forming signal to the set temperature,
wherein the timing is decided using the time obtained from the
calculating means and an expected time between the input of the
image forming signal and completion of the image formation.
11. An image forming apparatus according to claim 7, wherein, when
the expected time is shorter than the time obtained from the
calculating means, the timing is decided so that the control of the
temperature of the second image heating member for the inputted
image forming signal is started concurrently with the input of the
image forming signal.
12. An image forming apparatus according to claim 7, wherein, when
the expected time is longer than the time obtained from the
calculating means, the timing is decided so that the temperature of
the second image heating member is kept at the temperature lower
than the set temperature since the image forming signal is inputted
so that the temperature of the second image heating member and then
is raised to the set temperature before the completion of the image
formation.
13. An image forming apparatus according to claim 7, wherein, under
the first image forming condition, power application for heating
the second image heating member is turned off.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to an image forming apparatus
employing an electrophotographic system or the like, and more
specifically, to an image forming apparatus provided with a
plurality of fixing means for heat-fixing unfixed toner on a
recording material on a path for transporting the recording
material, thereby being capable of passing the recording material
through the fixing means on an upstream side with respect to a
transport direction of the recording material and then passing the
recording material through the fixing means on a downstream side
with respect to the transport direction.
[0003] 2. Related Background Art
[0004] Image forming apparatuses, such as printing machines,
copying machines, and printers, are becoming to be required to
output images having higher image quality. One indicator of image
quality of images is glossiness of printed images. In particular,
in the case of images such as photographs and illustrations, there
is such a tendency that images having higher glossiness are more
preferable.
[0005] Image glossiness is determined by fixing conditions, such as
fixing times, fixing temperatures, fixing widths, and fixing
pressures, of fixing apparatuses for fixing unfixed toner images
onto sheets such as paper and OHP films. Depending on the fixing
conditions at the time of fixation, fused states of the toner and
permeability of the toner with respect to the sheets vary, which in
turn changes the image glossiness. In ordinary cases, the image
glossiness is enhanced as the fixing time is elongated, as the
fixing temperature raises, as the fixing width is expanded, and as
the fixing pressure increases.
[0006] However, it is required not only to enhance the glossiness,
but also to reduce warmup time of the fixing apparatus and to
reduce power consumption thereof.
[0007] As a conventional technique, in order to achieve energy
saving, a short warmup time, and high glossiness at the same time,
an image forming apparatus including a plurality of fixing devices,
that are fixing means, is devised. From a viewpoint of energy
saving, in such the image forming apparatus, power application to
some of the fixing devices may be suspended. For instance, Japanese
Patent Application Laid-Open No. H07-271226 discloses an image
forming apparatus including a plurality of image heating devices
(fixing devices) and reduces power consumption by driving at least
one of the image heating devices at a set temperature and not
driving each remaining image heating device at the time of standby.
Further, Japanese Patent Application laid-Open No. 2002-372882
discloses a construction in which a plurality of image heating
devices are provided, power application to at least one of the
plurality of image heating devices is turned off when a glossy mode
is set, and power is applied to all of the plurality of image
heating devices when a non-glossy mode is set. With the
construction described above, image heating devices, whose
frequencies of use are low, are rarely supplied of power
application.
[0008] In the case of an image forming apparatus, into which a
plurality of image forming jobs during image forming operation, if
the construction includes a plurality of image heating means as
described above, there occur the following problems.
[0009] In an image forming operation, it is preferable, from a view
point of power consumption reduction, that a plurality of image
heating means are not used, for example, during image forming job
execution, application of power to image heating means not used in
this image formation is turned off or an amount of the power
applied to the image heating means is reduced. However, when a new
image forming job that uses all of the plurality of image heating
means is inputted during this image forming job, if power
application to place the image heating means not used at the time
of the input of the new job under an image heatable state is
started to maintain the image heating means under the image
heatable state, the longer the currently executed job is performed,
the longer the time taken before the new job is started becomes,
leading to a loss of energy. Conversely, when the power application
for obtaining the image heatable state is started at the time of
the start of the new job, a wait time is elongated. Therefore, it
is desirable that in such a case, a time, during which the image
heatable state is maintained, be shortened as much as possible
while shortening the wait time.
SUMMARY OF THE INVENTION
[0010] An object of the present invention is to start the new job
with a short wait time while reducing power consumption even if a
new job that uses all of the image heating means is inputted during
an image forming operation in which not all of image heating means
are used.
[0011] Another object of the present invention is to provide an
image forming apparatus including: a first image heating member for
heating an image on a recording material;
[0012] a second image heating member for heating the image on the
recording material heated by the first image heating member;
[0013] image forming condition selection means for making a
selection from among a first image forming condition, under which
the image on the recording material is heated by the first image
heating member without being heated by the second image heating
member, and a second image forming condition under which the image
on the recording material is heated by the first image heating
member and then is heated by the second image heating member;
[0014] first temperature control means for controlling a
temperature of the first image heating member;
[0015] second temperature control means for controlling a
temperature of the second image heating member to a set temperature
during image formation under the second image forming condition and
capable of controlling the temperature of the second image heating
member to a temperature lower than the set temperature in image
formation under the first image forming condition;
[0016] decision means for, in a case where an image forming signal
corresponding to the second image forming condition is inputted
during a job of image formation under the first image forming
condition, deciding a timing to start control of a temperature of
the second image heating member to said set temperature on the
basis of the amount of processes which are necessary until
completing the job.
[0017] The other objects of the present invention will become
apparent from the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] FIG. 1 is a schematic construction diagram of an image
forming apparatus in an embodiment of the present invention;
[0019] FIG. 2 is an enlarged view of a fixing apparatus portion
having a tandem construction;
[0020] FIG. 3 is a block diagram showing a control system for the
image forming apparatus;
[0021] FIG. 4 is a flowchart of control of the fixing apparatus
during image formation;
[0022] FIG. 5 is a diagram (first diagram) showing the control of
the fixing apparatus during image formation in a time-series
manner;
[0023] FIG. 6 is another diagram (second diagram) showing the
control of the fixing apparatus during image formation in a
time-series manner; and
[0024] FIG. 7 is a flowchart showing a comparison of process
conditions.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
First Embodiment
(1) Image Forming Apparatus
[0025] FIG. 1 is a schematic construction diagram of an example of
an image forming apparatus according to the present invention.
(Overall Construction of Image Forming Apparatus)
[0026] First, an overall construction of the image forming
apparatus will be described together with an image forming
operation with reference to FIG. 1. Note that FIG. 1 is an overall
schematic cross-sectional explanatory diagram of the image forming
apparatus according to this embodiment.
[0027] In the image forming apparatus in this embodiment, an image
reading portion 2 is provided in an upper portion of an apparatus
main body 1, an image forming portion 3 is provided below the image
reading portion 2, and a recording material transport portion 4 is
provided below the image forming portion 3.
[0028] The image reading portion 2 applies light from a light
source 2a to an original placed on an upper surface of the
apparatus, reads reflected light from the original with a line
sensor 2d through mirrors 2b and a reading lens 2c, converts a
result of the reading into a digital signal, and transmits the
digital signal to the image forming portion 3.
[0029] In the image forming portion 3, four image forming stations
Y, M, C, and K are disposed in parallel along a rotation direction
of an intermediate transferring belt 6 that is wrapped around a
drive roller 5a, a driven roller 5b, and an inner transfer roller
5c and rotates in an arrow direction. The image forming stations
form toner images in yellow (Y), magenta (M), cyan (C), and black
(K), respectively, in the stated order in the rotation direction of
the intermediate transferring belt 6. Note that those four image
forming stations are different from one another only in colors of
the formed toner images and have the same construction.
[0030] Here, the construction of the image forming stations will be
described by taking, as an example, the construction of the yellow
image forming station Y. A charger 8, a scanning optical apparatus
9, a developing device 10, and a cleaning portion 11 for removing
toner remaining on a photosensitive drum 7, which is an image
bearing member opposed to the intermediate transferring belt 6, are
disposed around the photosensitive drum 7. A toner replenishing
device 10a for replenishing the developing device with toner is
also provided.
[0031] With this construction, at the time of image formation, a
surface of the photosensitive drum 7 that is rotated is uniformly
charged by the charger 8 and light corresponding to image
information is applied from the scanning optical apparatus 9 onto
the charged photosensitive drum 7, thereby forming an electrostatic
latent image. This latent image is visualized through toner
development by the developing device 10 and a toner image obtained
as a result of the visualization is primarily transferred onto the
intermediate transferring belt 6 that is rotated through bias
application to a primary transfer member 12.
[0032] By separately performing the toner image transfer for images
in yellow, magenta, cyan, and black in succession, a color image is
transferred to the intermediate transferring belt 6.
[0033] In synchronization with the image formation described above,
a recording material is transported from the recording material
transporting portion 4 to a secondary transfer portion. That is, a
recording material is transported from a cassette 13 loaded into a
lower portion of the apparatus to the secondary transfer portion by
transport rollers 14. Then, a bias is applied to a secondary outer
transfer roller 15 at the secondary transfer portion, thereby
transferring the toner image on the intermediate transferring belt
6 onto the recording material. The recording material, onto which
the toner image has been transferred, is introduced into a fixing
apparatus A including two fixing devices (image heating means) that
are a first fixing device 22 and a second fixing device 23 and
serving as an image heating apparatus having a tandem construction,
passes through the first fixing device 22 and the second fixing
device 23 in succession, and is subjected to a heat-pressure
fixation processing for an unfixed toner image. This fixing
apparatus A will be described in detail in the next section
(2).
[0034] It should be noted here that in FIG. 1, three image position
reading detecting portions 18 for detecting position information of
the intermediate transferring belt 6 having the same construction
are disposed at three locations that are a back side, the center,
and a front side in a widthwise direction of the intermediate
transferring belt 6.
[0035] With this construction, before the image forming apparatus
performs image formation, an image of a "+" mark is formed at a
predetermined target position on the intermediate transferring belt
6 at each image forming station and the position of the image of
the "+" mark (hereinafter referred to as "registration mark") is
read by the image position reading detecting portions 18. Then, an
image position displacement amount concerning each parameter on the
intermediate transferring belt 6 of the image formation position of
the image formed at each image forming station is detected and
automatic correction is made by correction means.
(2) Fixing Apparatus A
[0036] FIG. 2 is an enlarged view of the fixing apparatus A portion
having a tandem construction including two fixing devices that are
the first fixing device 22 and the second fixing device 23 arranged
in series. The first fixing device 22 and the second fixing device
23 are arranged on an upstream side and a downstream side,
respectively, in a recording material transport direction. The
first fixing device 22 and the second fixing device 23 of this
embodiment are each a fixing device adopting a heat roller
system.
1) First Fixing Device 22
[0037] In the first fixing device 22, there are provided a fixing
roller (fixing upper roller) 22a serving as a first image heating
member and a pressurizing roller (fixing lower roller) 22b serving
as a first pressurizing member.
[0038] The fixing roller 22a is obtained by, for instance, forming
an elastic layer made of silicon rubber or the like on a
cylindrical core metal made of Al or the like and further forming a
release layer, such as a PFA tube, on a surface of the elastic
layer. This fixing roller 22a includes a fixing heater 22c therein,
such as a halogen lamp, serving as a heat generator.
[0039] The pressurizing roller 22b is obtained by, for instance,
forming a silicon rubber layer on a core metal and coating a
surface of the silicon rubber layer with a release layer such as a
PFA tube. The pressurizing roller 22b is brought into pressure
contact with the fixing roller 22a at a predetermined pressing
force, thereby forming a fixing nip portion N1 having a
predetermined width (size in the recording material transport
direction).
[0040] The fixing roller 22a is rotationally driven by a drive
system (not shown) in a clockwise direction indicated with an
arrow. The pressurizing roller 22b rotates following to the
rotation of the fixing roller 22a. Further, a thermistor 22d
serving as a temperature detecting member is provided to
contactingly or non-contactingly oppose the fixing roller 22a. The
fixing roller 22a is heated through heat generation by the fixing
heater 22c to which power is supplied from a power supply portion
(not shown). A surface temperature of the fixing roller 22a is
detected by the thermistor 22d and information showing the detected
temperature is fed back to a control portion that is first control
means. The control portion controls power supply from the power
supply portion to the fixing heater 22c so that the fixing roller
surface temperature shown by the information fed back from the
thermistor 22d becomes a predetermined fixing temperature (set
temperature) which is 200.degree. C., in this embodiment.
2) Second Fixing Device 23
[0041] In the second fixing device 23, there are provided a fixing
roller 23a serving as a second image heating member and a
pressurizing roller 23b serving as a second pressurizing
member.
[0042] The fixing roller 23a is obtained by, for instance, forming
an elastic layer made of silicon rubber or the like on a
cylindrical core metal made of Al or the like and further forming a
release layer, such as a PFA tube, on a surface of the elastic
layer. This fixing roller 23a includes a fixing heater 23c therein,
such as a halogen lamp, serving as a heat generator.
[0043] The pressurizing roller 23b is obtained by, for instance,
forming a silicon rubber layer on a core metal and coating a
surface of the silicon rubber layer with a release layer such as a
PFA tube. The pressurizing roller 23b is brought into pressure
contact with the fixing roller 23a at a predetermined pressing
force, thereby forming a fixing nip portion N2 having a
predetermined width.
[0044] The fixing roller 23a is rotationally driven by a drive
system (not shown) in a clockwise direction indicated with an
arrow. The pressurizing roller 23b rotates following to the
rotation of the fixing roller 23a. Further, a thermistor 23d
serving as temperature detecting means is provided to contactingly
or non-contactingly oppose the fixing roller 23a. The fixing roller
23a is heated through heat generation by the fixing heater 22c to
which power is supplied from a power supply portion (not shown). A
surface temperature of the fixing roller 23a is detected by the
thermistor 23d and information showing the detected temperature is
fed back to a control portion that is second control means. The
control portion controls power supply from the power supply portion
to the fixing heater 23c so that the fixing roller surface
temperature shown by the information fed back from the thermistor
23d becomes a predetermined fixing temperature which is 190.degree.
C., in this embodiment.
[0045] It is preferable that the set temperature of the first image
heating member be higher than the set temperature of the second
image heating member because the first image heating member is
required to fix an unfixed toner image on a recording material.
[0046] A fixing flapper 24 is provided between the first fixing
device 22 and the second fixing device 23 and serves as selection
means for switching a recording material course switching. The
control portion performs control in accordance with the properties
(image data/materials/settings) of jobs so that the fixing flapper
24 is driven to a first switching position, at which the recording
material P which has passed through the first fixing device 22 is
guided to a recording material transport path 25 in which the
recording material P is introduced into the second fixing device
23, and a second switching position at which the recording material
P which has passed through the first fixing device 22 is guided to
a recording material transport path 26 in which the recording
material P detours around the second fixing device 23.
[0047] The image forming apparatus according to the present
invention has a first image forming condition, under which heating
by the first fixing device is performed while heating by the second
fixing device is not performed, and a second image forming
condition under which both of the heating by the first fixing
device and the heating by the second fixing device are
performed.
[0048] For instance, in the case of a job using glossy paper as the
recording material or in the case of a glossy image mode (second
image forming condition) that requires image glossy, the control
portion switches the fixing flapper 24 to the first switching
position, thereby introducing the recording material P which has
passed through the first fixing device 22 into the second fixing
device 23 through the recording material transport path 25 and
subjecting the recording material P to a total of two fixation
processings by the first fixing device 22 and by the second fixing
device 23. The recording material introduced into the second fixing
device 23 has already passed through the first fixing device 23 and
is placed under a toner fixed state, so by further passing the
recording material through the second fixing device 23, it becomes
possible to securely realize stabilized fixability and desired
glossiness regardless of the material of the recording material and
image data.
[0049] On the other hand, in the case of a non-glossy image mode
(first image forming condition) in which glossy is not required,
the control portion switches the fixing flapper 24 to the second
switching position, thereby guiding the recording material P which
has passed through the first fixing device 22 to the recording
material transport path 26, in which the recording material P
detours around the second fixing device 23, and subjecting the
recording material P only once to the fixation processing by the
first fixing device 22. It is possible to make a selection from
among the glossy mode and the non-glossy mode through input using
an operating portion of the image forming apparatus or the
like.
[0050] In this embodiment, switching between the first image
forming condition and the second image forming condition is
performed based on glossy but the present invention is not limited
to this and the switching may be performed with reference to a
thickness of the recording material. For instance, fixation is
performed under the first image forming condition in the case of
plain paper and is performed under the second image forming
condition in the case of a thick sheet that requires a large
quantity of heat.
[0051] (3) Control System for Image Forming Apparatus
[0052] 1) FIG. 3 is a block diagram showing an example of an
overall control system for the image forming apparatus. In the
figure, a control portion (controller) 200 is composed of a CPU
200a, a ROM 200b, a RAM 200c, and the like and centralizedly
controls a copy sequence based on a program stored in the ROM
200b.
[0053] On the operating portion 219, a key input portion including
a copy mode setting key, a copy number setting key, a copy
operation start key, a copy operation stop key, a fixation power
saving key (hereinafter referred to as "power saving key") that is
adjusting means for adjusting an amount of electric power supply to
the second fixing device 23, a reset key that returns an operation
mode to a standard state, a glossiness setting key used to
designate glossiness of output images, and the like and a display
portion, such as an LED display or a liquid crystal display, for
displaying an operation mode setting state and the like are
disposed.
[0054] When the power saving key on the operating portion 219 is
pressed down, supply of electric power to the second fixing device
23 is stopped. Alternatively, a method may be used with which when
the power saving key is depressed, the second fixing device 23 is
set at a temperature that is lower than a set fixing temperature at
the time of image heating. To be more specific, for instance, the
second fixing device 23 is set at 200.degree. C. at the time of
image heating and is set at 100.degree. C. when the power saving
key is operated. In this case, a plurality of temperatures may be
set for the case where the power saving key is operated.
[0055] A first temperature control means will be described
hereinafter. In the embodiment, the first temperature control means
consists of CPU200a. The thermistor 22d detects the surface
temperature of the fixing roller 22a of the first fixing device 22.
A value obtained through A/D-conversion of the detected surface
temperature by an A/D converter 201 is inputted into the controller
200. The controller 200 controls power application to the heater
according to the detection value of the thermistor 22d so that the
surface temperature of the fixing roller 22a of the first fixing
device 22 assumes a predetermined value (set fixing
temperature).
[0056] A second temperature control means will be described
hereinafter. In the embodiment, the first temperature control means
consists of CPU200a. The thermistor 23d similarly detects the
surface temperature of the fixing roller 23a of the second fixing
device 23. A value obtained through A/D-conversion of the detected
surface temperature by an A/D converter 203 is inputted into the
controller 200. The controller 200 controls power application to
the heater according to the detection value of the thermistor 23d
so that the surface temperature of the fixing roller 23a of the
second fixing device 23 assumes a predetermined value (set fixing
temperature).
[0057] A high voltage portion 205 performs control of a high
voltage unit 206 that applies predetermined potentials to various
sites in the main body image output portion 1 such as a charging
system composed of a primary charger, a transfer charger, and the
like, and a developing apparatus.
[0058] A motor control portion 207 controls drive of various motors
208 such as a stepping motor.
[0059] A DC load control portion 209 controls drive of a solenoid
of the fixing flapper 24, a solenoid of a post-fixation flapper 28,
the photosensitive drum 17, the fixing rollers 22a and 23a of the
first and second fixing devices 22 and 23, respectively, a fan, and
the like.
[0060] Sensors 210 for detecting jamming of the recording material
and the like, send signals to be inputted into the control portion
200.
[0061] An AC driver 211 controls AC power supply to an AC load 212,
such as a light source 7, and fixing heaters 22c and 23c of the
first and second fixing devices 22 and 23, respectively. Also, the
AC driver 211 detects abnormalities of the light source 7, the
fixing heaters 22c and 23c, and the like and sets a main switch 216
having a shutoff function under an off state when detecting any
abnormality.
[0062] A DC power supply 215 supplies DC power to the controller
200 and the like. Here, AC power inputted from a power plug 218 is
inputted into the DC power supply 215 through a door switch 217 and
the main switch 216.
[0063] A feeding deck 4 is a feeding apparatus for increasing the
number of recording materials that can be stacked and is connected
as an option.
[0064] An editor 221 for inputting position information for
trimming, masking processing, and the like is connected as an
option.
[0065] A feeder 3 for automatically setting a plurality of
originals is connected as an option.
[0066] A sorter 5 for sorting discharged recording materials is
connected as an option.
[0067] In this embodiment, first control means for controlling a
temperature of the first image heating member and second control
means for controlling a temperature of the second image heating
member are included in the same control portion. However, as a
matter of course, the present invention is not limited to this
construction and a construction, in which a plurality of control
portions are provided, is also applicable.
[0068] 2) Next, control of the first and second fixing devices 22
and 23 when a first image forming job request is accepted and an
image forming operation is started will be described with reference
to FIGS. 4 to 6. Here, it is assumed that the power saving key on
the operating portion 219 is already pressed down and electric
power supply to the second fixing device 23 is stopped (turned
OFF).
[0069] FIGS. 5 and 6 are each a drawing in which control of the
first and second fixing devices 22 and 23 in the case where the
first image forming job is already started is shown in a time
series manner. FIG. 4 is a flowchart showing the control in that
case.
[0070] In FIGS. 5 and 6, the vertical axis represents a fixing
temperature and the horizontal axis represents time. In order to
perform image formation in response to the first image forming job
request, the temperature of the fixing roller 22a of the first
fixing device 22 is set at a fixing target temperature during image
formation. In this embodiment, the fixing target temperature is
200.degree. C. Under circumstances in which no electric power is
supplied to the heat source 23c of the fixing roller 23a of the
second fixing device 23 and the fixing roller 23a assumes
approximately the same temperature as an ambient temperature (which
varies depending on a use state of the second fixing device 23), a
second image forming job is inputted through pressing down of the
copy operation start key on the operating portion 219 or input of a
print signal by a user. As a result, the control portion 200 judges
that a second image forming job request is received (step S320 of
FIG. 4). When the control portion 200 judges that no second image
forming job request is received, polling is performed to wait until
it is judged that a second image forming job request is received
(step S320).
[0071] When it is judged that a second image forming job request is
received, it is next judged whether process conditions satisfy at
least one of predetermined conditions (step S321). As will be
described later, in this step, it is judged under which one of the
first image forming condition and the second image forming
condition the second image forming job request should be
processed.
[0072] When the control portion 200 judges in step S321 that the
process conditions satisfy none of the predetermined conditions and
the second image forming job request should be processed under the
first image forming condition, it is waited until a time T that is
a time interval between a second image forming job request
reception timing and first image forming job completion has elapsed
(step S322).
[0073] Next, it will be described hereinafter about decision means
for deciding a timing to start control of a temperature of the
second image heating member to said set temperature on the basis of
a process which is necessary until completing the job. In the
embodiment, the decision means consists of a CPU 200a.
[0074] When the control portion 200 judges in step S321 that the
process conditions satisfy at least one of the predetermined
conditions and the second image forming job request should be
processed under the second image forming condition, comparison of
the time T and a time Tup with each other is performed (step S324).
Here, as shown in FIGS. 5 and 6, the time T is an assumed time
interval between the second image forming job request reception
timing and the first image forming job completion and the time Tup
is a time calculated by calculating means, such as a CPU, that is,
a time taken by the fixing roller 23a to rise from a temperature at
the time of the second image forming job request reception to the
fixing target temperature after electric power supply to the heat
source 23c of the second fixing device 23 is started. In this
embodiment, the time T is calculated from an amount of remaining
image formation and an amount of processing executable per unit
time. Also, the time Tup is calculated from a temperature of the
second heating member at the time of the input, the fixing target
temperature, and input electric power. The time T and the time Tup
are each an assumed time, so there occurs no problem even when they
deviate from an actual time to some extent. In the embodiment, the
amount of processes which are necessary until completing the job is
the amount of remaining image formation processes at the time of
the second image forming signal being inputted. Moreover, the
amount of processes which are necessary until completing the job
may be a count value, which is determined in advance by counting
time until completing the first image forming job.
[0075] When it is judged in step S324 that the time T is longer
than the time Tup, that is, when, as shown in FIG. 5, the time
taken by the fixing roller 23a of the second fixing device 23 to
reach the fixing target temperature is shorter than the time
interval between the image signal input and the first image forming
job completion, it is waited until a time T-Tup has elapsed (step
S325). When the time T-Tup has elapsed, electric power supply to
the heat source 23c of the second fixing device 23, that is,
transition of the second fixing device 23 to an image heatable
state is started (step S326).
[0076] As a result of the operation described above, at a timing at
which the first image forming job is completed, the fixing roller
23a of the second fixing device 23 reaches the fixing target
temperature, so it becomes possible to uninterruptedly start the
second image forming job, which prevents lowering of
productivity.
[0077] On the other hand, when it is judged that the time T is
shorter than the time Tup (step S324), that is, when, as shown in
FIG. 6, the first image forming job is completed before the fixing
roller 23a of the second fixing device 23 reaches the fixing target
temperature, the electric power supply to the heat source 23c of
the second fixing device 23 is started instantly (step S327). That
is, approximately concurrently with the input, control of the
temperature of the second fixing device for image formation is
started. When it is judged that the fixing roller 23a of the second
fixing device 23 reaches the fixing target temperature (step S328),
an image forming operation is started. It is impossible to realize
desired fixability and glossiness before the fixing roller 23a of
the second fixing device 23 reaches the fixing target temperature,
so even after the first image forming job is completed, the second
image forming job is prohibited for a time Tup-T.
[0078] Next, a flow of the comparison of the process conditions and
the predetermined conditions with each other in step S321 to judge
whether the electric power supply to the heat source 23c of the
second fixing device 23 should be started will be described with
reference to FIG. 7. Through this flow, it is judged whether the
inputted job is a job corresponding to the first image forming
condition or a job corresponding to the second image forming
condition.
[0079] First, when, in step S310, it is judged that the recording
material passed for use is a thick sheet or a coarse sheet, it is
judged that the second image forming condition is satisfied (step
S315). Then, the comparison flow is ended as it is. The kind of the
sheet material may be detected with reference to a setting made by
a user from the operating portion 219 or may be automatically
detected by a sensor, such as a CCD sensor or a photo interrupter,
at a feeding cassette. When the recording material is a thick sheet
or a coarse sheet, there is a possibility that the sheet will
absorb heat from the fixing roller 22a at the time of passage
through the first fixing device 22 and therefore it becomes
impossible to achieve high fixability. Therefore, when the
recording material is a thick sheet or a coarse sheet, it is
required to pass the recording material through the second fixing
device 23 in order to secure fixability.
[0080] Next, when, in step S311, the control portion 200 judges
that glossy is required for image data, it is judged that the
second image forming condition is satisfied (step S315). Then, the
comparison flow is ended as it is.
[0081] For instance, image data accumulated in an image memory is
subjected to image area separation or the like to detect a ratio
between image data and character data and when an image data ratio
is high, it is judged that glossy is required. Alternatively, the
operating portion 219 may include a selection portion for allowing
a user to make an output image glossiness selection from among, for
instance, output of high gloss images and output of low gloss
images and the judgment as to whether glossy is required may be
made with reference to a setting made by the user from this
selection portion. In ordinary cases, satisfactory fixability is
achieved by merely passing the recording medium bearing an unfixed
toner image through the first fixing device 22 provided on an
upstream side of the transport path but it is possible to realize
high glossiness by further passing the recording medium through the
second fixing device 23 provided on a downstream side. Therefore,
it is required to judge whether high glossiness is required for
image data.
[0082] Next, when, in step S312, the control portion 200 judges
that an ambient temperature is not over a predetermined
temperature, it is judged that the condition is satisfied (step
S315). Then, the comparison flow is ended as it is. The higher the
ambient temperature is, the more favorable fixability of an image
with respect to a sheet becomes, so it becomes unnecessary to pass
the sheet through the second fixing device 23. Here, it is possible
to arbitrarily set the predetermined temperature. Therefore, it is
required to judge whether the ambient temperature is over the
predetermined temperature.
[0083] Next, when, in step S313, it is judged that the sheet
temperature is not over a predetermined temperature, it is judged
that the second image forming condition is satisfied (step S315).
Then, the comparison flow is ended as it is. It is possible to
detect the sheet temperature by measuring a temperature of a sheet
fed from a feeding portion with a temperature sensor. The higher
the sheet temperature is, the more fixability of an image with
respect to the sheet becomes favorable, so it becomes unnecessary
to pass the sheet through the second fixing device 23. Here, it is
possible to arbitrarily set the predetermined temperature.
Therefore, it is required to judge whether the sheet temperature is
over the predetermined temperature. Further, in this embodiment,
the sheet temperature is detected but when image formation is
possible on both sides of the recording material, whether a
double-sided image forming operation is performed may be judged.
This is because, when a double-sided operation is performed, since
the sheet has already passed through the first fixing device 22 for
image fixation onto a surface, the sheet is heated to a high
temperature. Therefore, when such a double-sided image forming
operation is not performed, it is judged that the condition is
satisfied (step S315). Then, the comparison flow is ended as it
is.
[0084] When, as a result of the process condition comparison
described above, it is judged that the second image forming
condition is not satisfied (step S314). Then, the comparison flow
is ended as it is.
[0085] In this embodiment, a construction has been described in
which when the power saving key is pressed down, the power
application to the second fixing device is not performed at least
during execution of the first image forming job. Further, it is
possible to obtain the same effect with a construction in which a
plurality of energy saving modes having different standby set
temperatures, even if the waiting is performed at one of the
standby set temperatures lower than the set temperature at the time
of image heating of the second fixing device.
[0086] Also, in this embodiment, a construction has been described
in which the power application to the second fixing device is not
performed when the second fixing device is not used. However, a
construction is also possible which has a power saving key with
which it is possible to select whether at least during execution of
an image forming job that does not use the second fixing device,
unless an image signal corresponding to the second fixing device is
inputted, the second fixing device is turned off or is placed under
a low set temperature waiting state.
[0087] Further, there occurs no problem even in the case of a
construction in which the first fixing device and the second fixing
device have a plurality of set temperatures during image heating.
In this case, for instance, depending on a level of glossiness
inputted into the image forming apparatus, the set temperature
during image heating of the second fixing device is changed. To be
more specific, for instance, the second fixing device is set at
200.degree. C. in the case of a high glossiness mode and is set at
180.degree. C. in the case of a middle glossiness mode. Here, the
number of set temperatures, to which the second fixing device is
switchable, may be increased.
[0088] Still further, there occurs no problem even in the case of a
construction in which the set temperature during image heating of
the first fixing device is changed depending on the kind of the
recording material. When glossiness control is performed, it is
preferable that the fixation state of the toner image on the
recording material after the recording material has passed through
the first fixing device be maintained constant regardless of the
kind of the recording material because it becomes possible to
enhance the accuracy of the glossiness control by the second fixing
device. In particular, for instance, the first fixing device is set
at 200.degree. C. in the case of plain paper, is set at 210.degree.
C. in the case of a thick sheet, and is set at 190.degree. C. in
the case of a thin sheet. As a matter of course, the number of set
temperatures may be increased from three in this example.
[0089] Further, in this embodiment, a construction using fixing
rollers has been described but it is possible to obtain the same
effect even with a construction using fixing belts or the like.
Further, each fixing roller is heated by a heater but the present
invention is not limited to this and it is possible to provide the
same effect even when the fixing roller is heated with an induction
heating system using a coil.
[0090] As described above, when electric power supply is performed
for only one of the plurality of fixing devices during first image
formation, in a case where a second image forming request, for
which all of the plurality of fixing devices need to be used, is
received, all of the plurality of fixing devices reach the fixing
target temperature immediately before the first image forming
operation is completed, thereby avoiding a waste of electric power,
so it is possible to maintain high productivity because the second
image forming operation is started immediately after the completion
of the first image forming operation.
[0091] Further, even if the first image forming operation is
completed before all of the plurality of fixing devices reach the
fixing target temperature, the second image forming operation is
prohibited until all of the plurality of fixing devices reach the
fixing target temperature, so it is possible to prevent fixation
failure due to fixation at a low temperature.
[0092] It should be noted here that the plurality of fixing devices
(fixing means) of the fixing apparatus having the tandem
construction are not limited to the fixing devices adopting the
heat roller system of the embodiment of the present invention.
Further, the number of the fixing devices is not limited to two and
may be increased to three or more.
[0093] As described above, according to the present invention, when
a new job in which all of the image heating members are used
inputted during image formation in which some of image heating
members are not used, it is possible to elongate a standby state of
each second image heating member, in which the second image heating
member is set at a low temperature, without causing a delay of
start of the new job.
Second Embodiment
[0094] Another embodiment will be described below. In the first
embodiment, the time Tup is obtained by detecting the temperature
of the second fixing device (output of the thermistor 23d) at the
time when the second image forming job is inputted and calculating
a time taken by the second fixing device to rise from the detected
temperature to the set temperature at the time of image
heating.
[0095] In this embodiment, however, a plurality of predetermined
set times are set, the temperature of the second fixing device
(output of the thermistor 23d) at the time when the second image
forming job is inputted is detected, and one of the set times is
selected in accordance with the detected temperature. For instance,
the set temperature at the time of image heating is 200.degree. C.
and the following temperature ranges are prepared for the
temperature of the second fixing device.
1) less than 30.degree. C.
2) 30.degree. C. or more and less than 70.degree. C.
3) 70.degree. C. or more and less than 120.degree. C.
4) 120.degree. C. or more
[0096] In this case, when the detected temperature is in the
temperature range 1), an image heatable state is started to be
maintained 30 seconds before an expected time for starting the
second image forming job. Also, when the detected temperature is in
the temperature range 2), the image heatable state is started to be
maintained 20 seconds before the expected time for starting the
second image forming job. Further, when the detected temperature is
in the temperature range 3), the image heatable state is started to
be maintained 10 seconds before the expected time for starting the
second image forming job. Still further, when the detected
temperature is in the temperature range 4), the image heatable
state is started to be maintained 5 seconds before the expected
time for starting the second image forming job.
[0097] With this construction, when a new job that uses all of the
image heating members is inputted during image formation that does
not use some of image heating members, it becomes possible to
elongate a standby state of each second image heating member, in
which the second image heating member is set at a low temperature,
without causing a delay of start of the new job using a simple
construction in which a time taken by the second fixing device to
rise from a temperature at the time when the new job is inputted to
the set temperature is not calculated.
[0098] As described above, according to the present invention, when
a new job that uses all of the image heating means is inputted
during an image forming operation that does not use some of image
heating means, it becomes possible to start the new job with a
short wait time while reducing power consumption.
[0099] Embodiments of the present invention have been described
above but the present invention is in no way limited to the
embodiments of the present invention and various modifications are
possible within the scope of the technical idea of the present
invention.
[0100] This application claims priority from Japanese Patent
Application No. 2005-112160 filed Apr. 8, 2005, which is hereby
incorporated by reference herein.
* * * * *